Gamma-ray burst afterglows

The origin of the X-ray afterglows of gamma-ray bursts has regularly been debated. We fit both the fireball-shock and millisecond-magnetar models of gamma-ray bursts to the X-ray data of GRB 130603B and 140903A. We use Bayesian model selection to answer the question of which model best explains the data. This is dependent on the maximum allowed non-rotating neutron star mass M TOV , which depends solely on the unknown nuclear equation of state. We show that the data for GRB140903A favours the millisecond-magnetar model for all possible equations of state, while the data for GRB130603B favours the millisecond-magnetar model if M TOV 2.3M . If M TOV 2.3M , the data for GRB130603B supports the fireball-shock model. We discuss implications of this result in regards to the nuclear equation of state and the prospect of gravitational-wave emission from newly-born millisecond magnetars.

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“…is used (e.g., Sari et al 1999;Zhang 2007). Here, t is the time since burst, α is the temporal index, and β is the spectral index.…”

Section: Fireball Modelmentioning

confidence: 99%

X-Ray Afterglows of Short Gamma-Ray Bursts: Magnetar or Fireball?

Sarin

Lasky

Ashton

2019

ApJ

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“…However, 10 of the 42 GRBs show shallower decay indices and we could not find a reasonable interpretation from the afterglow, neither in uniform ISM nor in wind medium. In addition, we also found that some of the optical shallow decay 1 The single power-law function is F(ν,t) ∝ t −α , where α is a single power-law index and the broken power-law function:…”

Section: Analysis and Resultsmentioning

confidence: 94%

“…steep decays, flares, and shallow decays) were found in many X-ray lightcurves. Those properties, thought to be connected to an active central engine, could be characterized by prompt emission from GRBs or a mixture of different emission components contributing to the observed X-ray emission [1]. In addition, the comparison of X-ray and optical light curves have clearly shown that the evolutions for the two wavelengths are generally different [2,3].…”

Section: Introductionmentioning

confidence: 99%

Exploring the Nature of Gamma-ray Burst Shallow Decay

Huang

Chiu

Urata

2012

Proceedings of Gamma-Ray Bursts 2012 Conference — PoS(GRB 2012)

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We have studied the optical temporal evolution of 42 Swift GRBs. Our investigation shows that most of the optical properties can be interpreted by the external shock model and implies that the observed optical emission originated from this model. However, of the 42 GRBs, 10 show shallow decay properties in their overall optical light curve. Further investigations into the 10 GRBs found that the corresponding shallow decay properties were also found in their X-ray light curve. Apart from GRB 050730, our results also indicate that most shallow decay orginates from the external shock in both X-ray and optical. We conclude that, for some bursts, the optical and X-ray shallow decay have an extrnal origin, but some bursts have different emission mechanisms.

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“…The presence of any knee in a decay series can be accounted for by recognizing that some isotope decay chains can have radioactive progeny with higher specific gamma activity than a parent nuclide. Other models have been proposed which tend to adhere to similar power law decay approximations (Zhang 2007). Even with all this, there are additional bumps and wiggles (Maienschein et al 1958) in these fission decay responses due to co-irradiated materials which can depend on interstitial materials (e.g., moderators and poisons), shielding and reflectors.…”

Section: Grb Time Evolutionmentioning

confidence: 99%

Nuclear criticality as a contributor to gamma ray burst events

Hayes¹

2013

Astrophys Space Sci

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-Most gamma ray bursts are able to be explained using supernovae related phenomenon. Some measured results still lack compelling explanations and a contributory cause from nuclear criticality is proposed. This is shown to have general properties consistent with various known gamma ray burst properties. The galactic origin of fast rise exponential decay gamma ray bursts is considered a strong candidate for these types of events. BackgroundThe Oklo uranium mine in South Africa is a place where the natural abundance of U235 was found to be consistently less than the 0.72% found everywhere else on the planet (with the remainder of the uranium being almost entirely U238). It was not until the excess isotopic distribution from the stable fission product decay nuclides was found that it was realized this was an ancient natural nuclear reactor (Cowan 1976). Because the half life of U235 is almost an order of magnitude smaller than that of U238, the ratio of U235 to U238 increases in reverse time. By going back far enough in time, the abundance of the two nuclides would become comparable. With sufficiently enriched uranium in the soil, addition of moisture from rain would then provide the necessary moderation for the earth to sustain a natural nuclear chain reaction until the heat would drive away the water and return the system to a subcritical state. This process is believed to have occurred over a billion years ago in central Africa (Fujii et al. 2000).If the Oklo reactor occurred naturally as a result of uranium created in supernovae (SN) events, it is not incredible to think that it could occur prior to accumulation into planetary form from other SN events. In other words, just after the SN creation of the uranium and transuranic isotopes, most of the already radioactive elements created will quickly decay into stable atoms leaving these fissile and fissionable isotopes close to their original abundance. Even if a large fraction of the Pu239 (which is fissile with a moderately long half life of just over 24 ka) were to decay away, there would still be almost the initial amount of U233 (which is fissile with a moderately long half life of just under 0.2 ma) with only a negligible fraction of the U235 having decayed away. If a gravitational accumulation of the SN excreta were to occur within some few years, a longer list of potential fissile isotopes could be present in the material including Pu241, Am243, Cm243, Cm245, Cm247, etc while the majority of the radioactive elements would still have decayed into stable isotopes. This presents a dynamic reactivity dependency in terms of the fissile nuclides generated which would be strongly dependent on the initial isotopic distribution source term.The model presented here has the potential to explain some of the highly varied nature of a portion of measured gamma ray bursts (GRBs). These include the random nature of the events in terms of their parametric values and ranges. Specifically many measured values of energy and time distributions, pulsing, and afterglows ...

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Gamma-ray burst afterglows

Cited by 32 publications

References 185 publications

X-Ray Afterglows of Short Gamma-Ray Bursts: Magnetar or Fireball?

X-Ray Afterglows of Short Gamma-Ray Bursts: Magnetar or Fireball?

Exploring the Nature of Gamma-ray Burst Shallow Decay

Nuclear criticality as a contributor to gamma ray burst events

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